1. Field of the Invention:
This invention relates a mechanical supercharger utilized in internal combustion engines, and more particularly to a mechanical supercharger wherein a relief control valve is accommodated.
2. Discussion of Background Art:
It is well known that a relief control valve may be generally adopted to control supercharging pressure in a mechanical supercharger. In a conventional supercharger with a relief control valve, as shown in FIG. 1, a surge tank 51 is connected to an intake manifold 58 of an internal combustion engine 55. A relief control valve 52 is disposed in the surge tank 51 so as to keep a suction air pressure in the surge tank 51 under a predetermined value. The relief air from the relief control valve 52 is returned to an upstream portion of the supercharger 53 or to an air cleaner 57 via a control conduit 54 that is separate from the supercharger 53. Numeral 56 indicates a carburetor.
In the above-mentioned conventional relief control system, however since the control conduit 54 is positioned outside of the supercharger 53 and the construction of the relief control valve 52 is complicated, there is a drawback that the device has a large size. Furthermore, in the conventional mechanical supercharger, noises are generated by discharge pulsations of the supercharging pressure released from the relief control valve. In addition, when the control conduit is disposed on the outside of the supercharger, there is a noise problem in that noise radiates from the control conduit. When the mechanical supercharger 53 is located downstream from the carburetor 56 as shown in FIG. 1, there will be a further problem in that gasoline vapors can leak out from the joints of the control conduit 54.